Grain dryer

ABSTRACT

The grain dryer disclosed herein is designed to eliminate the tendency of certain portions of the grain, particularly damp portions, to become lodged within the dryer thereby to give every kernel of grain an equal opportunity to come into contact with the drying regions of the dryer. For this purpose the dryer is provided with specially designed return channels and ports which act to regulate and ensure a continuous flow of grain entering the dryer mixing chamber where all the grain has an opportunity to be mixed together and thereafter elevated by means of an elevator which extends upwardly from the mixing chamber. The grain, after being elevated, is discharged adjacent the upper end of the elevator and allowed to spill outwardly over the grain. The return channels cause the grain to continually take a different course each time it passes over or through the drying regions of the dryer. Provision is made for heated air to pass through the dryer return channels thus assisting in effecting rapid drying of the grain.

United States Patent 1 Adams GRAIN DRYER [76] Inventor: Arnold L. Adams, 1944 Saint George Avenue, Saskatoon, Saskatchewan, Canada 22 Filed: Apr. 21, 1971 [2]] Appl. No.: 136,117

[30] Foreign Application Priority Data Aug. 7, 1970 Canada ..O90213 52 US. (:1 34/102 259/97 [51] Int. Cl ...F26b 25/00 [58] Field of Search 1.34/1 1, 102; 259/97 [56] References Cited UNITED STATES PATENTS 2,634,513 4/1953 Ladd et al. ..34/102 3,078,590 2/1963 Batterton et aLL ..34/lO2 Primary Exa mineF-Kenneth W. Sprague Assistant Examiner-James C. Yeung Att0rr eyFleit, Gipple & Jacobson 1 Apr. 17, 1973 ABSTRACT The grain dryer disclosed herein is designed to eliminate the tendency of certain portions of the grain, particularly damp portions, to become lodged within the dryer thereby to give every kernel of grain an equal opportunity to come into contact with the drying regions of the dryer. For this purpose the dryer is provided with specially designed return channels and ports which act to regulate and ensure a continuous flow of grain entering the dryer mixing chamber where all the grain has an opportunity to be mixed together and thereafter elevated by means of an elevator which extends upwardly from the mixing chamber. The grain, after being elevated, is discharged adjacent the upper end of the elevator and allowed to spill outwardly over the grain. The return channels cause the grain to continually take a different course each time it passes over or through the drying regions of the dryer. Provision is made for heated air to pass through the dryer return channels thus assisting in effecting rapid drying of the grain.

12 Claims, 7 Drawing Figures LEG'END HOT AIR DIRECTION OF GRAIN FLOW PATENTED 1 3.727. 558

SHEET 1 OF 4 INVENTOR ARNDLD L. ADAMS BY 97%, e 4,6046

ATTORNEYS PATENTEDAPRITIBB 3.72m 55s SHEET 2 BF 4 LEGEND HOT AIR DIRECTION OF GRAIN FLOW FIG. IA

PATENTED APR 1 7 I973 SHEET 3 [1F 4 FIG.3

FIG. 4

FIG.5'

PATENTEDAPR 1 11911 3', 727. 556

SHEET 0F 4 GRAIN DRYER BACKGROUND OF THE INVENTION This invention relates generally to dryers for particulate material, and especially to improvements in grain dryers.

It is well known in the art that grain dryers are virtually a necessity to any grain producer having a considerable amount of grain to harvest and who, due to adverse weather conditions, finds that his grain is not dry enough to store safely. A well designed grain dryer permits the producer to place damp or wet grain within his dryer and to continue the harvest while the dryer is left unattended to carry out its function. Grain dryers of this nature are usually equipped with a suitable automatic control means to eliminate overdrying of the grain.

In the past, various attempts have been made to design batch dryers and continuous flow dryers such that they are capable of properly drying the grain so that a uniform degree of moisture remains within each and every grain kernel at the end of the drying operation. Due to the design of most of these dryers, however, each and every grain kernel does not have an equal opportunity to pass over or remain within the heated drying means of the dryer sufficiently long as to properly effect removal of the moisture from within the grain. This is partly due to the fact that tough and damp grain does not flow readily; therefore, once the grain becomes partially dried within the drying chamber and re-circulation of such grain is effected, the drier portions of the grain have a tendency to return, upon recirculation, approximately to the same course of travel while the damper portions of the grain remain relatively dormant. Thus, the damper portions of the grain tend to become lodged in various areas of the dryer and hence do not have an opportunity to pass over or adjacent the drying regions of the equipment. This obviously results in non-uniform drying of the grain. In other cases the grain passes over the drying regions so rapidly that only the moisture from the exterior of the kernels is removed. The presence of moisture in the in- .terior of the grain kernels is difficult to detect since grain moisture testing apparatus responds to the surface moisture of the grain. Most tests will simply indicate that this grain has been dried such that it has the proper moisture content for safe storage. However, after the grain has been stored in bins for a period of time such that the moisture in the grain re-distributes itself uniformly, the grain upon being tested again with the same moisture testing apparatus will show an actual moisture level content which is considerably higher than that previously indicated.

SUMMARY OF THE INVENTION It is the primary object of the present invention to eliminate or at least substantially reduce, the above mentioned problem of some grain becoming overdried, and other grain remaining damp and, accordingly, the present invention provides a grain dryer having specialized means therein to entice the movement of all the grain being dried thereby to ensure that all portions of the grain have a substantially equal opportunity to come into contact with the heating medium being employed to effect drying.

In accordance with the present invention there is provided a dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, and an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts positioned on said sloping floor arranged to direct grain passing therethrough to said mixing region, said return ducts adapted to permit free passage of a controlled amount of grain therethrough. In the preferred form of the invention these ducts are constructed so that such grain may pass directly over said sloping floor in intimate contact with the heated air which, in operation, passes upwardly therethrough, as such grain passes through said ducts toward the mixing region. 7

In the preferred form of a dryer according to the invention, the perforated floor of the bin is of inverted conical configuration. The return ducts are located on this perforated surface and are designed in such a way that the flow of grain therethrough is unrestricted once it has passed an adjustable control gate located at the entrance of the return channel. In this way backing up of the grain within the return channels and choking thereof is eliminated. In addition, the gates or grain controls are fully adjustable at all times and are effective whether the drying chamber be completely filled with grain or almost empty.

The various features of the invention will become more apparent from the following description of a preferred embodiment and the appended claims.

BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS FIG. 1 is a cross-sectional view in elevation taken through the center of the drier;

FIG. 1A is a view essentially the same as FIG. 1 illustrating the paths taken by the circulating grain and the circulating gases for drying same;

FIG. 2 is a plan section view taken along line 2-2 in FIG. I above the sloping perforated floor, showing the layout of the grain return ducts, the housing containing the adjustable gates, the lower assembly, and the location of the lower grain return gates;

FIG. 3 is an enlarged cross-section view taken along line 3-3 in FIG. 2 of the above mentioned housing, showing the system used in adjusting the grain return gates to effect control of the grain returning to the centrally located auger;

FIG. 3A is a fragmentary plan section view taken along line 3A-3A in FIG. 3;

FIG. 4 is a plan of a section near the outer end of radially arranged grain return ducts.

FIG. 5 is a section showing the method of controlling the return gates.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The dryer shown in the drawings includes a chamber in the form of an upright cylindrical bin which can be constructed of either wood or metal. A conical roof 11 covers the entire bin, with the roof supports 12 placed upon the outer rim 13 of the bin in such a manner that any moisture collecting on the underside of the roof 14 will flow downwardly and dissipate on the outside of the bin 10.

A batch of grain G to be dried is placed within the bin through the hatch 15 in the roof or through the hole 16 in. a central location of the bin roof covered by. a removable roof cap 17. The approximate upper level of the batch is given by the dotted line L.

Within the interior of the bin is an inverted conicalshaped metal floor 18 having closely spaced perforations therein sized to permit passage of gas e.g., hot air, but not grain, therethrough, said floor sloping towards the central vertical axis of the bin. Perforated floors of this nature are known; see for example U.S. Pat. No. 2,634,513 issued Apr. 14, 1953 to Ledd et a1. Below the main level of the sloping perforated floor 18 is a mixing chamber 19 arranged such that all grain returning over the sloping floor 18 is channeled thereto. Ex-

' tending upwardly along the vertical central axis of the bin from the mixing chamber 19 is a vertical grain auger 21 which takes the grain from mixing chamber 19 at the lowermost part of the drier to the top of the drier where the grain is radially spread by means of a conical-shaped metal deflector 22 connected to the upper part of auger 21 just above the upper level of the gram.

A centrally located metal housing 23 is located at the bottom of the dryer and surrounds and encloses the lower section of a rotatable auger 21 just above mixing chamber 19. Grain entering housing 23 moves downwardly into mixing chamber 19 so that it may be picked up by the auger and elevated to the top of the dryer. Blending or mixing of the grain in the mixing chamber is assisted by virtue of the action of the rotating auger.

Extending towards central housing 23 from points spaced inwardly from the upright wall of the bin and entering into housing 23 are several radially arranged grain return ducts which slope downwardly towards the center of the bin. These ducts 20 are fastened to the sloping perforated floor 18 in equally spaced relation to one another as shown in FIG. 2. The floor of each duct 20 is, in effect, defined by the perforated floor 18 so that grain passing through these ducts has an excellent chance to come into intimate contact with heated gases passing through the perforated floor 18. Currents of heated air actually pass upwardly along the duct in opposition to the flow of grain therein as illustrated in FIG. 1A thus assisting the drying process. The upper inlet ends of ducts 20 are located a short distance from the bin walls and the lower exit ends of ducts 20 enter through housing 23. In operation, a controlled proportion of grain passes freely through the return ducts 20 and into the mixing chamber 19. The remainder of the grain passes directly into housing 23 and into mixing chamber 19 through openings 24a in the perimeter of the housing 23 disposed between the radially arranged return ducts 20. The flow of grain entering the central housing 23 between the return ducts 20 is controlled by means of a plurality of curved metal gates 24 mounted for vertical movement in metal guides welded to the side wall of the metal housing 23. Each gate 24 can be raised or lowered by means of a removable crank 25 which is attached to the shaft 26 upon which bevel gears 27 are mounted. The shaft 28 is threaded and inserted into a threaded bracket 29 welded to each gate 24 allowing complete control of the amount of grain passing into the mixing chamber 19.

The above mentioned radially arranged grain returns 20 which are attached to the perforated floor 18 are constructed of sheet metal and formed to act as a channel to permit grain to pass unrestricted therethrough to the lower section of the dryer and into the mixing chamber. At the uppermost or inlet end of each return duct 20, there is mounted a metal gate 30 retained within metal channels 31 which allow the gate to be adjusted upwardly or downwardly to control the flow of grain into housing 23. Fastened to each metal gate 30 is a bracket 32. One end of a shaft 33 is inserted through the bracket 32 and allowed to turn freely by means of two washers 34 and pins 35 inserted into the shaft 33. The shaft 33 is of such length that one end which is threaded will extend below the perforated floor 18. Under the floor supports 53 which acts as a fulcrum 35 is mounted a threaded bracket. On the end of the threaded shaft 33 is mounted a universal joint 36, from which a shaft 37 extends to the exterior of the bin 10 allowing a removable crank 25 to be placed which upon turning right or left will raise or lower the metal gates 30 within the grain returns 20.

It can be seen from the above that by adjusting the gates 24 and 30 that the desired proportions of grain can be made to flow into housing 23 through the openings 24a in the latter between the return ducts 20 and through the return ducts 20 themselves. In all cases, mixing of both portions of grain together in the mixing chamber 19 takes place before the grain is elevated by auger 21 and again redistributed. It will thus be seen that the grain is received in the mixing chamber from widely spaced points in the dryer i.e., through the openings 24a controlled by gates 24 located adjacent the central axis of the dryer (and hence close to the mixing chamber) and through the inlet ends of return ducts 20 which are radially spaced outwardly of the first mentioned ports (and the mixing chamber) by a substantial distance.

By properly regulating these gates the problem of damp grain becoming lodged within the bin can be substantially eliminated and the grain can be evenly dried.

Around the exterior of the lower portion of auger housing 21 there is disposed a metal sleeve 40 slightly larger than the auger housing 21. Fastened to the sleeve 40 is a threaded metal bracket 41 into which a threaded shaft 42 is screwed. At the upper end of this shaft 42 and mounted within a U-shaped bracket 43 is a bevel gear 27. A horizontally disposed shaft 44 extends to the exterior of the bin 10, upon which is mounted a bevel gear 27 which meshes with the gear 27 placed on the vertical shaft 42. This raises or lowers the metal housing 40 surrounding the auger 21 and thus controls the flow of grain entering the vertical auger 45 from mixing chamber 19. A removable crank 25 is placed on the end of the horizontal shaft 44 which extends beyond the exterior of the bin wall 10 allowing the housing 40 to be raised or lowered over the vertical auger 45.

The vertical auger 45 may be powered by means of an electric motor 46 placed at the uppermost end of the auger, or by means of a hydraulic motor attached at either end of the shaft 47 upon which the auger blade 48 is attached, thus elevating grain to be dried within the bin.

Hot air is forced from a heater (oil or gas fired) and fan arrangement 56 of conventional construction, placed outside the bin 10, into the hot air chamber 50 which is defined by the exterior walls 10, the floor of the bin 51 and the conical perforated floor 18. From within this hot air chamber 50, the hot air, the temperature of which is thermostatically controlled, can pass upwardly through the perforations in the floor 18, through the grain return ducts 20, and through the body of grain which is moving in the. opposite direction to the flow of air.

The grain passing through the return control gates 30, continues to flow downwardly to the central area of the dryer by means of gravity. The proportion of grain entering the return ducts can be controlled by the gates so that each and every kernel of grain comes directly in contact with the heated air emitted from the heated air chamber 50 thus assuring that all the grain is evenly dried. All the grain is heated to the same temperature throughout the entire batch and is recirculated through the dryer several times. The amount of moisture to be extracted from the grain can be terminated at any time. All grain upon being heated to extract moisture from within the kernels should be tempered or cooled to the temperature of the air outside the dryer before placing in storage. The grain can be quickly cooled to the outside atmospheric condition by turning off the supply of fuel to the-heating unit and allowing the fan to continue to operate. Meanwhile the grain continues to recirculate within the drying bin as described in the preceding paragraphs. Cooling and tempering of the grain is accomplished very rapidly due to the bin 10 being made such that it retains the cool air within the drying chamberfor a relatively long period of time. During this cooling period grain continues to circulate over the perforated floor 18, down through the grain channels and gates, and is again mixed, elevated and allowed to spread over the above mentioned deflector. Each time, the grain comes in contact with the cool air which has replaced the hot air from the burner, thus effectively cooling the grain.

The grain, upon being dried and conditioned, can be removed by means ofa loading auger 52 with the lower end placed intothe mixing chamber 19 and operated when the desired degree of dryness is obtained.

While the invention has been shown and described in one particular form, it is possible that structural changes may be made without departing from the spirit of the invention and it is accordingly desired that the patent protection extend and cover all matters falling within the scope of the appended claims.

lclaim:

1. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor of a generally inverted cone shaped configuration extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts being positioned on said floor in spaced generally radially arranged relation and being adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region.

2. The dryer according to claim 1 further including control means at the inlet ends of the return ducts to control the amounts of grain passing therethrough.

3. The dryer according to claim 2 wherein the means for admitting grain into the mixing region further comprises means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region said further openings being re1ative ly closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom.

4. The dryer according to claim 3 wherein said further series of openings have control means associated therewith to regulate the flow of grain therethrough into the mixing region.

5. The dryer according to claim 3 further including blower and heater means for supplying heated air to the underside of said sloping floor to effect drying of grain supported thereon.

6. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, the means for admitting grain into the mixing region further comprising means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom, said further series of openings having control means associated therewith to regulate the flow of grain therethrough into the mixing region.

7. The dryer according to claim 6 wherein the control means for both the return ducts: and the further series of passages comprise adjustable gate means.

8. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor of a generally inverted cone-shaped configuration extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts being positioned on said floor in spaced generally radially arranged relationship with the return ducts being adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, the dryer further characterized in that said means for admitting grain into the mixing region further comprises means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region, said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom, and a housingjust above said mixing region and communicating therewith, said further series of openings being defined in said housing, and said return ducts also being arranged to discharge into said hous- 9. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged-to direct grain passing therethrough to said mixing region, said return ducts adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, and wherein the floor of each said return duct is defined by said sloping floor such as to permit the heated air to pass upwardly directly into said duct through the openings in said floor and into direct contact with the grain passing through said duct. 10. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, and wherein the return ducts are located on said sloping floor with said ducts being constructed so that such grain may pass directly over said sloping floor in intimate contact with the heated air which, in operation, passes upwardly therethrough, as such grain passes through said ducts.

11. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor ofa generally inverted cone-shaped configuration extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts being located adjacent said floor in spaced generally radially arranged relation with said ducts being adapted to permit free passage of a controlled flow of grain therethrough to the mixing region.

12. The dryer according to claim 11 wherein the means for admitting grain into the mixing region further comprises means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom. 

1. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor of a generally inverted cone-shaped configuration extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts being positioned on said floor in spaced generally radially arranged relation and being adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region.
 2. The dryer according to claim 1 further including control means at the inlet ends of the return ducts to control the amounts of grain passing therethrough.
 3. The dryer according to claim 2 wherein the means for admitting grain into the mixing region further comprises means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom.
 4. The dryer according to claim 3 wherein said further series of openings have control means associated therewith to regulate the flow of grain therethrough into the mixing region.
 5. The dryer according to claim 3 further including blower and heater means for supplying heated air to the underside of said sloping floor to effect drying of grain supported thereon.
 6. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grAin thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, the means for admitting grain into the mixing region further comprising means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom, said further series of openings having control means associated therewith to regulate the flow of grain therethrough into the mixing region.
 7. The dryer according to claim 6 wherein the control means for both the return ducts and the further series of passages comprise adjustable gate means.
 8. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor of a generally inverted cone-shaped configuration extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts being positioned on said floor in spaced generally radially arranged relationship with the return ducts being adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, the dryer further characterized in that said means for admitting grain into the mixing region further comprises means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region, said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom, and a housing just above said mixing region and communicating therewith, said further series of openings being defined in said housing, and said return ducts also being arranged to discharge into said housing.
 9. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therEthrough to said mixing region, said return ducts adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, and wherein the floor of each said return duct is defined by said sloping floor such as to permit the heated air to pass upwardly directly into said duct through the openings in said floor and into direct contact with the grain passing through said duct.
 10. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts adapted to permit free passage of a controlled flow of grain therethrough toward the mixing region, and wherein the return ducts are located on said sloping floor with said ducts being constructed so that such grain may pass directly over said sloping floor in intimate contact with the heated air which, in operation, passes upwardly therethrough, as such grain passes through said ducts.
 11. A dryer for grain and like materials wherein drying is effected by passage of heated air therethrough comprising: a bin, a sloping floor of a generally inverted cone-shaped configuration extending about the entire lower portion of the bin adapted to support a batch of grain thereon and having a plurality of openings therein adapted to permit heated air to pass upwardly therethrough, said floor sloping towards the lower end of said bin, means defining a mixing region at said lower end of said bin arranged to receive grain from the sloping floor, an elevator positioned in said bin extending from the mixing region upwardly to a discharge point adjacent the top of the bin to convey grain upwardly from the mixing region to the discharge point, means for admitting grain into said mixing region including a plurality of downwardly sloping return ducts arranged to direct grain passing therethrough to said mixing region, said return ducts being located adjacent said floor in spaced generally radially arranged relation with said ducts being adapted to permit free passage of a controlled flow of grain therethrough to the mixing region.
 12. The dryer according to claim 11 wherein the means for admitting grain into the mixing region further comprises means defining a further series of openings for admitting grain supported on said sloping floor into said mixing region said further openings being relatively closely spaced to the mixing region and said inlet ends of the return ducts being spaced a substantial distance outwardly therefrom. 